Utility vehicles used in a commercial or industrial environment may include lift equipment, including portable material lifts, telehandlers, scissor lifts, telescopic and articulating booms. These vehicles typically have a hydraulic system that acts to propel the vehicle and operate the work function, such as a lift platform, of the vehicle. The hydraulic system drives the vehicle by controlling the vehicle propulsion, vehicle braking, and vehicle steering. One or more pumps of the hydraulic system are typically driven by an internal combustion engine or other prime mover in the vehicle.
These vehicles often are provided with four-wheel drive, with hydraulic motors providing torque to drive the wheels to provide traction for the vehicle and to propel the vehicle. In a conventional system, the hydraulic traction system or traction circuit divides the fluid flow from the pump and sends one portion to the hydraulic motors associated with the front wheels and front axle and another portion to the hydraulic motors associated with the rear wheels and rear axle. This provides generally equal flow to the hydraulic motors with the motors and wheels turning at the same speed, regardless of the steer angle of the vehicle. During a turn, the vehicle wheels need to turn at different speeds based on their location on the vehicle, and the conventional front/rear split in the hydraulic traction circuit leads to inefficiencies in the hydraulic circuit and in the vehicle as one or more wheels may lose traction and slip or skid in a turn.